142 lines · c
1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * pps-ldisc.c -- PPS line discipline4 *5 * Copyright (C) 2008 Rodolfo Giometti <giometti@linux.it>6 */7 8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt9 10#include <linux/module.h>11#include <linux/serial_core.h>12#include <linux/tty.h>13#include <linux/pps_kernel.h>14#include <linux/bug.h>15 16static void pps_tty_dcd_change(struct tty_struct *tty, bool active)17{18 struct pps_device *pps;19 struct pps_event_time ts;20 21 pps_get_ts(&ts);22 23 pps = pps_lookup_dev(tty);24 /*25 * This should never fail, but the ldisc locking is very26 * convoluted, so don't crash just in case.27 */28 if (WARN_ON_ONCE(pps == NULL))29 return;30 31 /* Now do the PPS event report */32 pps_event(pps, &ts, active ? PPS_CAPTUREASSERT :33 PPS_CAPTURECLEAR, NULL);34 35 dev_dbg(pps->dev, "PPS %s at %lu\n",36 active ? "assert" : "clear", jiffies);37}38 39static int (*alias_n_tty_open)(struct tty_struct *tty);40 41static int pps_tty_open(struct tty_struct *tty)42{43 struct pps_source_info info;44 struct tty_driver *drv = tty->driver;45 int index = tty->index + drv->name_base;46 struct pps_device *pps;47 int ret;48 49 info.owner = THIS_MODULE;50 info.dev = NULL;51 snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index);52 snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index);53 info.mode = PPS_CAPTUREBOTH | \54 PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \55 PPS_CANWAIT | PPS_TSFMT_TSPEC;56 57 pps = pps_register_source(&info, PPS_CAPTUREBOTH | \58 PPS_OFFSETASSERT | PPS_OFFSETCLEAR);59 if (IS_ERR(pps)) {60 pr_err("cannot register PPS source \"%s\"\n", info.path);61 return PTR_ERR(pps);62 }63 pps->lookup_cookie = tty;64 65 /* Now open the base class N_TTY ldisc */66 ret = alias_n_tty_open(tty);67 if (ret < 0) {68 pr_err("cannot open tty ldisc \"%s\"\n", info.path);69 goto err_unregister;70 }71 72 dev_info(pps->dev, "source \"%s\" added\n", info.path);73 74 return 0;75 76err_unregister:77 pps_unregister_source(pps);78 return ret;79}80 81static void (*alias_n_tty_close)(struct tty_struct *tty);82 83static void pps_tty_close(struct tty_struct *tty)84{85 struct pps_device *pps = pps_lookup_dev(tty);86 87 alias_n_tty_close(tty);88 89 if (WARN_ON(!pps))90 return;91 92 dev_info(pps->dev, "removed\n");93 pps_unregister_source(pps);94}95 96static struct tty_ldisc_ops pps_ldisc_ops;97 98/*99 * Module stuff100 */101 102static int __init pps_tty_init(void)103{104 int err;105 106 /* Inherit the N_TTY's ops */107 n_tty_inherit_ops(&pps_ldisc_ops);108 109 /* Save N_TTY's open()/close() methods */110 alias_n_tty_open = pps_ldisc_ops.open;111 alias_n_tty_close = pps_ldisc_ops.close;112 113 /* Init PPS_TTY data */114 pps_ldisc_ops.owner = THIS_MODULE;115 pps_ldisc_ops.num = N_PPS;116 pps_ldisc_ops.name = "pps_tty";117 pps_ldisc_ops.dcd_change = pps_tty_dcd_change;118 pps_ldisc_ops.open = pps_tty_open;119 pps_ldisc_ops.close = pps_tty_close;120 121 err = tty_register_ldisc(&pps_ldisc_ops);122 if (err)123 pr_err("can't register PPS line discipline\n");124 else125 pr_info("PPS line discipline registered\n");126 127 return err;128}129 130static void __exit pps_tty_cleanup(void)131{132 tty_unregister_ldisc(&pps_ldisc_ops);133}134 135module_init(pps_tty_init);136module_exit(pps_tty_cleanup);137 138MODULE_ALIAS_LDISC(N_PPS);139MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");140MODULE_DESCRIPTION("PPS TTY device driver");141MODULE_LICENSE("GPL");142